The present invention relates to a shirred sausage casing and a process for its manufacture. In particular, the invention relates to a shirred sausage casing having a seam region which is helically twisted about said casing to provide improved casing properties.
The formation of a shirred tubular casing having one or several seams running along the longitudinal axis of the casing, wherein the edge regions of the edge zones running along the longitudinal axis are glued to one another, is described, for example, in European patent application No. 0,037,543. In connection with the teachings of U.S. Pat. Nos. 3,988,804 and 4,185,358, this publication describes a device which is used for shirring sausage casings possessing areas of increased thickness in the form of glued seams. By means of this particular shirring device, the tubular casing is automatically twisted during the shirring of the casing. According to the procedure, the glued seam zone of a tubular casing is arranged, in a helically wound manner, about the longitudinal axis of the shirred tubular casing. However, the process results in the casing having less than 10 helical turns of the seam zone per 10 m of tube length. Such a ratio, which reflects the desire for a high shirring ratio, is insufficient for present needs. Moreover, it is impossible in this way to achieve a reproducible lead of the helically wound seam zone. Also, the hollow space in the interior of the concertinaed tubing does not have a circular cross section, due to the fact that at least part of the relatively thick seam zone is displaced into the hollow space during shirring.
It has also been proposed, for example in European patent application No. 81 109 120.6, to twist a sausage casing with a glued seam helically during shirring by using a shirring device in accordance with any of U.S. Pat. Nos. 2,819,488, 3,619,854, 3,594,857 or 3,766,603. The number of turns per 10 m of tube length varies between 0.5 and 10. More than 10 turns per 10 m of tube length cannot be achieved by helically twisting the tube during shirring. When internal or external tangentially acting forces are applied to the concertinaed tubing, producing a rotary movement of the tubing relative to the mandrel, the danger that the tubular casing may be damaged due to the strain exerted on it is relatively great and, therefore, a complicated shirring technique is required.